class Solution {
public:
    int jumpFloorII(int number) {
        //if(number == 1)
         //   return 1;
        
        //return 2*jumpFloorII((number-1));
        
        //因为是二倍关系，所以可以直接左移一位得到结果
        return 1 << (number-1);
        
    }
};

